Water heating apparatus



1966 B. E. MCCLANAHAN 3,

WATER HEATING APPARATUS Filed April 20, 1964 3 Sheets-Sheet 1 wmm l -30dam-{1% [1 L 3 INVENTOR.

BERNARD E. Mc CLANAHAN BY PM M ATTORNEYS 3, 1966 B. E. MCCLANAHAN3,267,909

WATER HEATING APPARATUS Filed April 20, 1964 5 Sheets-Sheet 2 THERMOSTAT5 INVENTOR.

BERNARD E. McCLANAHAN BY am ATTORNEYS Aug. 23, 1966 B. E. M CLANAHAN3,267,909

WATER HEATING APPARATUS Filed April 20, 1964 3 Sheets-Sheet 3 INVENTOR.BERNARD E. McCLANAHAN BYF/IAW a/ L ATTORNEYS United States Patent3,267,909 WATER HEATING APPARATUS Bernard E. McClanahan, La Habra,Calif., assignor to Ace Tank and Heater Company, Santa Fe Springs,Calif., a corporation of California Filed Apr. 20, 1964. Ser. No.361,146 12 Claims. (Cl. 122250) This invention relates to liquid heatingsystems and more particularly to water heating apparatus for the heatingof swimming pools and the like.

Most swimming pools have incorporated therewith, in the installedequipment associated with the pool for the proper maintenance thereof,one or more pool heaters. Such heaters are needed in all but the warmsetof climates in order to heat the pool in cool weather, notably in thespring and fall, so that the useful period of swimming pool enjoymentmay be extended beyond the more or less limited summer season. A typicalarrangement involves a water heater which may utilize a gas burner inconjunction with tubing or a similar arrangement for transferring heatfrom the burning fuel to the water flowing through the heater. Theheater is usually mounted in a pump house in conjunction with the usualpumping and filtering apparatus associated with the swimming poolinstallation. The heater is coupled to the pumping and waterrecirculating system by means of suitable valving arrangements and isgenerally thermostatically controlled for automatic operation. With thevalve coupling the heater to the water recirculating portion of thesystem set to pass a portion of the water being recirculated by the pumpthrough the heater, the recirculated water is warmed there by andreturned to the pool.

It will be clear that the heating of a pool of even moderate sizerequires a considerable amount of heat, and it is therefore veryimportant that a water heater structure of efficient design be provided.For example, a typical swimming pool of dimensions 15 feet by 36 feetwith a depth of 8 feet at one end sloping to 3 feet at the other end maycontain approximately 25,000 gallons. Without considering the loss ofany heat from the pool, it requires the absorption of 200,000 Britishthermal units (B.t.u.s) of heat to raise the temperature of such aquantity of water 1 Fahrenheit. With the additional consideration of theheat losses by conduction to the ambient surroundings and byevaporation, it will be seen that a very substantial amount of heat mustbe injected into a normal swimming pool in order to raise thetemperature by any suitable extent, as when the pool is first used atthe beginning of the summer or merely to replace the heat which is lostovernight. Even in summertime, the temperature of the normal uncoveredswimming pool may drop by 2 F. overnight due to heat transfer andevaporation. It is not unusual that the water heater employed forheating a typical backyard swimming pool may require a greater capacitythan the residential heating unit employed for the residence associatedtherewith. In order that the cost of operating a swimming pool heatingunit will not be prohibitive, it is essential that the pool heatingapparatus be as efficient as possible.

Heretofore there has been one particular problem which has plagued thedesigners of apparatus for use in heating swimming pools. When suchheating apparatus is coupled to the recirculating system for a swimmingpool, it will be appreciated that the water entering the heatingapparatus from the pool is at swimming pool temperature, conventionally75 or less. In passing through the swimming pool heater, the water istypically heated to a temperature between 100 and 120 and returned tothe portion of the recirculating system leading back to the pool, whereit becomes mixed with the recirculating water and the pool a fuelburner.

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and itself becomes cooled as it gradually raises the temperature of thepool. The combustion process in the Water heater apparatus develops asignificant amount of Water vapor which undesirably exhibits a tendencyto condense on the cooler portion of the water tubing conducting therelatively cold water being received from the pool. Such condensation isquite undesirable, as it tends to foul the water heating apparatus fromthe collection of dirt and trapped deposits on the burner and alsocontributes to the corrosion of the water heating apparatus and anyother equipment with which it comes in contact. In addition, thecondensation dripping off and running out of the water heater gives riseto complaints that the heater has developed a leak when such is not thecase. Various attempts have been made to solve the particular problem ofcondensation in water heating apparatus of the type described Withoutnotable success. For example, some structures provided for this purposeincorporate fire tube, as contrasted with water tube, construction, butit has been found that the efiiciency of heat transfer with such anarrangement is less than the water tube type. Other attempts have beenmade to employ siphoning tubes or the like which will mix a portion ofthe heated water leaving the water heater with the cold water enteringthe heater, thus raising the temperature of the inlet water above thepoint at which condensation is likely to form. These attempts have notbeen particularly effective and they involve the installation ofadditional piping and other apparatus which undesirably increases thecost and complexity of the water heating apparatus provided. In caseswhere condensation is controlled by reducing the rate of water fiowthrough the heater, the water is heated to an unnecessarily hightemperature, thereby increasing the heat losses and reducing theefficiency of operation.

It is therefore a general object of the present invention to provide animproved water heating apparatus for swimming pools and the like.

It is a more specific object of the present invention to eliminate thecondensation of water from the combustion gases in a swimming pool waterheater.

It is a further object of the present invention to provide an improvedtype of water heater apparatus for swimming pools and the like whicheliminates the problem of water condensation normally encounteredtherein.

A still further object of the present invention is to improve theefliciency of heat transfer in water heating apparatus designed for usewith swimming pools or the like.

In brief, particular arrangements in accordance with the presentinvention comprise a water tube member of a particular shape mountedwithin an enclosure adjacent The water tube member incorporates aplurality of fins over a substantial portion of its length, and it maybe coiled in what may be described as an hourglass shape with thecentral portion of the hourglass configuration substantial-1y blocked bya bafile member and the outer portions of the hourglass configuration atopposite ends thereof being positioned adjacent the walls of theenclosure. With such an arrangement, the combustion gases from theburner are forced to pass outwardly between adjacent coils of the finnedtubing member in the lower section of the hourglass configuration, sincethe passage directly through the center of the configuration is blockedby the baffle member. In the upper section of the hourglassconfiguration, the combustion gases are forced to pass inwardly betweenadjacent coils of the finned tubing member because the uppermost coil ispositioned adjacent the interior wall of the enclosure and thus blocksthe passage of the combustion gases past this'region on the outside ofthe hourglass configuration. The combustion gases in passing from theburner to the exhaust stack of the water heater are thus forced to passback and forth twice through the water tube structure while beingmaintained in intimate contact with the fins and tubing of the structurefor maximum heat transfer.

The tubing member comprises over at least a portion of its length adouble walled structure adapted for the flow of water within an interiorsection separated from the outer, finned Wall by a space which is alsofilled with water. In one particular arrangement in accordance with theinvention the double walled structure extends throughout substantiallythe entire length of the tubing member and may be fabricated byinserting a length of relatively small diameter tubing within the lengthof relatively larger diameter tubing to which the fins are aifixed. Theinterior section of the tubing is closed for substantially its entirelength except at the lower end thereof Where it is permitted tocommunicate with the interior of the larger diameter tubing by means ofa header or blind manifold which blocks the orifice of the largerdiameter tubing while permitting reversal of water flow from the smallerdiameter tubing to the larger diameter tubing at that point. At theupper end of the water tube configuration, a T-shaped couplingarrangement is provided which permits separate coupling to the inner andouter tube sections from associated water conduits. With thisarrangement, water from the recirculating pump is introduced into thesmaller tubing so as to fiow downwardly through the smaller tubing as itis coiled within the outer tubing member in the hourglass configurationto the lower end thereof where it reverses direction and flows backupwardly through the outer tubing member between the outer wall of thesmaller diameter tubing and the inner wall of the larger diameter tubingto the T-section member and then through piping which will return theheated water to the pool. In accordance with an aspect of the invention,siphoning of the water tube is prevented by providing a small hole inthe coupling to the inner tube so that air which may get into therecirculating system is permitted to bypass the water tube. Thisprotects the water tube from being emptied inadvertently and therebydamaged when the heater is lit.

In a second particular arrangement in accordance with the invention thedouble walled structure of the tubing member extends over only a minorportion of the length thereof and may be fabricated by insertingapproximately ten feet of relatively smaller diameter, inner tubingwithin the lower end of an approximately thirty-foot length of largerdiameter, outer finned tubing coiled in the hourglass configuration asdescribed. In this arrangement, water to be heated is introduced forfull flow at the lower end of the inner tube. A suitable coupling memberis employed having an apera-ture providing a small passage between theinner tube and the outer tube at the water inlet portion. This smallpassage permits a limited flow of water in the region between the innerand outer tubes, thus ensuring that this water is heated to the properelevated temperature without overheating when the burner'is operating.This relatively slower moving water in turn conducts heat to the morerapidly flowing water in the inner tube and effectively preheats themain flow of water in the inner tube which is maintained out of contactwith the walls of the outer tube until its temperature has been raisedabove the condensation point. By means of such arrangements inaccordance with the invention, the cold water as it enters the waterheater is substantially surrounded by heated water near the inlet end ofthe water tube structure so that no contact with the combustion gases ispossible and the problem of condensation of water therefrom is entirelyobviated. A further advantage accruing from this particular arrangementin accordance with the invention is an increase in the efiiciency ofheat transfer to the water being heated by the water heating apparatus.It is well known that the eflicieney of heat transfer between two mediais a function of the absolute temperature diiference between the two.Thus, the lower the temperature of the water in the water tubestructure, the more efficient the transfer of heat from the combustiongases to the water being heated. There is no advantage in raising thewater in the water tube structure to a high temperature (such as nearthe boiling point) since this will increase the heat losses encounteredas the water is returned to the pool, and the hot water is immediatelycooled anyway as it is mixed with the main body of water in the pool.Therefore, particular arrangements in accordance with the inventionwhich provide for the preheating of the inlet water by means ofdouble-walled passages which are in heat transfer relationship permitthe more rapid flow of water through the heater and thus serve toprevent the water near the outlet portion of the structure from beingraised to such an elevated temperature. As a result, more heat isextracted from the combustion gases, thus increasing the efliciency ofapparatus in accordance with the invention while positively preventingthe formation of moisture'by condensation on the water tube by ensuringthat the temperature of the tube at all exposed portions is maintainedabove the condensing temperature.

A better understanding of the invention may be had from a considerationof the following detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 depicts generally a typical swimming pool installation with arecirculating filtration and heating system in which the invention maybe employed;

FIG. 2 is an elevation view of a particular water heater arrangement inaccordance with the invention;

FIG. 3 is a sectional view of the particular arrangement in accordancewith the invention shown in FIG. 2, taken along the line 3-3 thereof;

FIG. 4 is a perspective representation, partially broken away, of aportion of the arrangement in accordance with the invention depicted inFIGS. 2 and 3 and showing particular details thereof;

FIG. 5 is a representation of a particular portion of the arrangementshown in FIGS. 2 and 3;

FIG. 6 is a representation, partially broken away, of a secondparticular arrangement in accordance with the invention which may beemployed in the water heater of FIG. 2; and

FIG. 7 is a view, partially broken away, of a particular portion of thearrangement of FIG. 2 for use in conjunction with the structure of FIG.6.

FIG. 1 represents schematically a general installation of a swimmingpool and the associated water filtration and heating equipment normallyinstalled therewith. As shown in FIG. 1, a swimming pool 10 is coupledby a drain line 12 to a trap 14, a pump 16, a filter 17, a heater 18,and a return line 20. A pair of valves 21 and 22 are shown in the linesto and from the heater 18 in order to regulate or cut off the flow ofwater to and from the heater 18 as desired. Other valves, drain lines,electrical connections and the like which may be associated with typicalinstallations have been omitted for the sake of simplicity. In thearrangement shown in FIG. 1 the heater 18 is connected directly to thepump 16 and in parallel with the filter 17. The purpose of thisarrangement is to develop the maximum available pressure across theheater 18 so that a more rapid flow of water through the heater 18 maybe achieved, thereby enhancing the efiiciency of heat transfer withinthe heater 18. However, an alternative arrangement may be employed, asis customary, wherein the heater 18 is connected downstream from thefilter 17 and a bypass line with a valve in it is provided so that watermay be made to flow throughthe heater after passing through the filteror it may be permitted to bypass the heater as desired.

One particular embodiment in accordance with the invention which may beutilized as the heater 18 in the arrangement shown in FIG. 1 is depictedin FIGS. 2 and 3, FIG. 3 being a sectional view of FIG. 2 taken alongline 33. As shown in FIGS. 2 and 3, the water heater 18 may comprise ahousing 22 in the form of a substantially upright cylinder having anouter jacket 24 and an inner jacket 26, with a flue 28 connected to theupper side of the housing 22. The inner jacket 26 defines a combustionchamber containing a burner 30 in a central location at the bottom ofthe housing 22 and a water tube member 32 coiled in a substantiallyhourglass configuration. The water tube member 32 is arranged with itsuppermost and lowermost coils substantially against the inner jacket 26to prevent combustion gases from passing outside the water tube memberat these points. A baflie member 34 in the form of a dished plate ispositioned near the narrow diameter of the hourglass configuration ofthe water tube member 32 and serves to block combustion gases frompassing directly through the center of the hourglass configuration.Thus, by means of this arrangement, combustion gases from the burner 30are directed upwardly and forced to pass between adjacent coils of thewater tube member 32 in the lower portion of the hourglass configurationto the outside thereof, then past the position of the baffle member 34and back to the inside of the hourglass past the adjacent coils of thewater tube member 32 in the upper portion of the hourglass configurationfrom whence they are exhausted through the flue 2%. The water tubemember 32 is shown in greater detail in FIG. 4 as comprising an innertube 36 positioned within an outer tube 37 and arranged for thebi-directional flow of water through the water tube member 32. The outertube 37 is covered with a plurality of fins 38 which project into theregion of the combustion gases in the water heater 18 for improvedefficiency of heat transfer to the water passing within the tube 37. Thelower end of the water tube member 32 is closed off by a blind manifold40 which permits the free passage of water from the inner tube 36 to theouter tube 37 and provides for the reversal of flow therein. The blindmanifold 40 is provided with a cap 42 which blocks the end of themanifold 40. An auxiliary outlet is provided by a threaded section 43 towhich a valve 41 (such as is shown in FIG. 2) may be coupled to providea means for draining or cleaning the water tube member 32 as desired.

At its upper end, the water tube member 32 is provided with a similarlyshaped manifold or coupling member 44 and an associated couplingarrangement, shown in greater detail in FIG. 5. As shown in FIG. 5, awater inlet fitting 47 in the form of a T is connected directly to apipe 46 which is arranged, upon assembly, to slip over the uppermost endof the inner tube 36. A second T 45, coupled to the first T 47 byappropriate fittings and arranged to extend around the pipe 46 isprovided for coupling directly onto the threaded end of the manifold 44.Water is thus permitted to flow out of the water tube member 32 via theoutlet T 45. A thermostat 48 for controlling the operation of the heater18 in accordance with the temperature of the swimming pool water and thecontrol setting thereof is shown connected to the water inlet T 47. Ahigh temperature cut-off device 50 is shown coupled to the manifold 44in a position to sense the temperature of the water leaving the watertube member 32. The high temperature cut-off device 50 is connected to aheater fuel valve in conventional fashion for cutting off the supply offuel to the burner 30 whenever the temperature of the water in the watertube member 32 exceeds a safe limit.

In accordance with an aspect of the invention, the pipe 46 is providedwith a small hole 52 as shown. The hole 52 is an anti-siphon hole andserves to prevent water from draining out of the water tube member 32 inthe event that air gets into the water recirculating system. Thus, thisarrangement insures that water is maintained within the water tubemember 32 so that there is no danger of the burner 30 operating with adry water tube and thereby damaging the heating apparatus.

The fabrication of the water tube member 32 may be readily accomplishedby first inserting within a relatively straight length of finned outertubing 37, a length of inner tubing 36 which is approximately 1 footlonger than the outer tubing 37. The increased length of the innertubing 36 is to provide the desired length to be curved into the uppercoupling member 44 which is attached to the upper end of the outer tube37 so as to permit coupling of the inner tube 36 to the coupling pipe46. It is desirable to match the water flow capacity of the inner tube36 to that of the outer tube 37 with the inner tube 36 in place. In onepreferred embodiment, a 31-foot length of one-half inch ID. byfiveeighths inch O.D. smooth copper tubing was inserted in a 30-footlength of finned tubing having an inside diameter of one inch. Theentire arrangement was then coiled in the hourglass configuration shownin FIG. 4 and suitable coupling members 40 and 44 were attached toopposite ends thereof to provide the water tube member 32. Otherarrangements having different dimensions may be employed for swimmingpool heaters of various capacities.

In operation, water from the swimming pool 10 is supplied directly fromthe pump 16 to the water inlet coupling 47 where its temperature issensed by the thermostat 48, and the burner 30 is operated in accordancewith the temperature setting of the thermostat 48-. Water from the waterinlet coupling 47 passes directly to the pipe 46 and thence to the innertube 36. As the inlet water flows down and around the water tube member32 within the inner tube 36, water is simultaneously flowing upwardlyand around through the outer tube 37 surrounding the inner tube 36.Assuming that the burner 30 is operating to heat the swimming pool,water adjacent the surface of the outer tube 37 receives heat directlyfrom the fins 38 of the water tube member 32 from the burning gases inthe combustion chamber within the inner jacket 26. As this water isheated, some of its heat is transferred to the inner tube 36 and thewater flowing therein. Consequently, by the time the water in the innertube 36 has reached the lower end thereof adjacent the blind manifold40, its temperature is raised sufficiently that it is above the point ofcondensation of the water vapor in the combustion gases from the burner30. Thus, as the water reverses direction at the blind manifold 40 andreturns upwardly through the outer tube 37, there is no tendency for thecondensation of water on the outside of the tube 37. Moreover, theeffective preheating of the inlet water within the inner tube 36 beforeit is passed to the outer tube 37 not only eliminates the previouslyexperienced problem of condensation of water vapor at the inlet end ofthe water tube member 32 but also permits a more rapid flow of waterthrough the water tube member 32 so that heat is more efficientlytransferred to the water from the combustion gases within the heater 18.

Another particular arrangement in accordance with the invention isrepresented in FIG. 6 which shows a water tube member 32' coiled in aconfiguration similar to that of FIG. 4. The water tube member 32 ofFIG. 6 comprises an outer tube 37 covered over substantially its entirelength with a plurality of fins 38 for the eflicient transfer of heatfrom the combustion gases Within the heater 18 to the water flowingthrough the tube 37. The outer tube 37 is shown containing an inner tube36' which begins near the lower end of the Water tube member 32' andextends through only a portion of the outer tube 37, this extent beingapproximately /3 of the full length of the outer tube 37 in thearrangement depicted in FIG. 6. The water tube member 32' is providedwith upper coupling member 44 and a lower coupling member 44'. Detailsof the lower coupling member 44 and the conduit elements attachedthereto may be seen in FIG. 7, which shows a reducing coupling 45connected to the coupling member 44 and having a sleeve-like conduit 46arranged to engage the inner tube 36' at the lower end thereof. An

inlet coupling 47 to which a thermostat 48 for sensing the watertemperature may be attached is shown connected to the conduit 46'extending outwardly from the reducing coupling 45. An opening 53 isprovided in the wall of the conduit 46' to permit a limited flow ofwater from the conduit 46' to the region outside the inner tube 36' butwithin the members 44' and 45'.

The water tube member 32' is designed for installation in the heater 18of FIGS. 2 and 3 in the manner shown in connection with the water tubemember 32. Thus, the how of the combustion gases and the transfer ofheat therefrom to the outer tube 37 proceeds in similiar fashion.However, in the operation of the particular arrangement of the inventionincluding the water tube member 32 of FIG. 6, water is introduced viathe coupling arrangement of FIG. 7 at the lower end of the water tubemember 32', from whence it flows upwardly through the water tube member32' and is taken from the heater 18 at the upper end of the water tubemember 32 for eventual return to an associated swimming pool or otherwater storage arrangement. This particular arrangement in accordancewith the invention presents a reduced opposition to the flow of water,since the inner tube 36 through which most of the water is directedextends for only a limited distance along the coiled configuration ofthe water tube member 32. Thus a water heater utilizing thisconfiguration may be operated under relatively less pressuredifferential and may advantageously be installed at the outlet of thefilter in a swimming pool water recirculating system, rather than havingto be coupled directly at the outlet side of the recirculating pump. Inaccordance with an aspect of the invention, the opening 53 permits alimited flow of water to the outer tube 37 along the outside of theinner tube 36', thus permitting water to flow through thiscircumferential region so that the Water therein is not raised to anundesirably high temperature where hot spots or boiling may occur. Atthe same time, heat is transmitted through the water in thecircumferential region of the Water tube member 32' between the innertube 36 and the outer tube 37 to the inlet Water flowing at fullcapacity through the inner tube 36', where it effectively preheats thisinlet water to a temperature above the condensation point. Thus, whenthe preheated inlet water Within the inner tube 36' is introduced to theouter tube 37 at the upper end of the inner tube 36', it is above thecondensation temperature so that the condensation of water vapor alongthe outer tube 37 is effectively eliminated. Accordingly, as in the caseof the particular arrangement depicted in FIG. 4, the effectivepreheating of the inlet Water within the inner tube 36' before it ispassed to the outer tube 37 eliminates the problem of water vaporcondensation on the water tube member and as a result makes possible amore rapid flow of water through the water tube member without suchcondensation, thus achieving a more efiicient transfer of heat from thecombustion gases Within the heater 18 to the Water being heated.

Although there have been described above particular arrangements ofwater heating apparatus in accordance with the invention for the purposeof illustrating the manher in which the invention may be used toadvantage, it will be appreciated that the invention is not limitedthereto. Accordingly, any and all modifications, variations orequivalent arrangements falling within the scope of the annexed claimsshould be considered to be a part of the invention.

What is claimed is:

1. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a housing of substantially cylindrical form, aburner positioned at the base of said housing, a flue at the top of saidhousing, and a water tube member arranged in a vertically disposedhourglass configuration between the burner and the flue with the top andbottom portions of said hourglass configuration adjacent the housing toblock the passage of combustion gases thereby and having a baflle memberpos tioned across the narrow portion of the hourglass configuration,said water tube member including concentric portions for thebidirectional conduction of water therein and having a blocking memberterminating the lower end of the Water tube member in a manner such asto permit the reversal of water flow thereat within the water tubemember and further having a coupling member connected to the upper endthereof for admitting water to flow into an inner concentric portion ofthe Water tube member and for permitting the flow of water out of theouter concentric portion of said water tube member.

2. Water heating apparatus in accordance with claim 1 wherein saidblocking member includes a valve which may be opened for draining orcleaning said Water tube member.

3. Water heating apparatus in accordance with claim 1 wherein said watertube member further comprises a plurality of fins positionedsubstantially along its length with said water tube member being coiledin said hourglass configuration so that the corresponding fins ofadjacent coils of the water tube member are substantially touching todefine the spacing between the adjacent coils.

4. The Water heating apparatus in accordance with claim 1 wherein saidwater tube member comprises a pair of tubes one within the other, thewater conducting capacity of tubes one within the other, the waterconducting capacity of the inner tube being substantially matched to theWater conducting capacity of the outer tube with the inner tube inposition within the outer tube.

5. A bidirectional water tube member for use in a swimming pool waterheater or the like comprising a finned outer pipe containing an innerpipe along substantially its entire length, the Water flow capacity ofthe inner pipe being substantially matched to the Water flow capacity ofthe portion of the outer pipe with the inner pipe in place therein, theWater tube member being coiled in a substantially hourglassconfiguration so as to control the direction of combustion gases in apredetermined flow over substantially the entire extent of said watertube member.

6. A bidirectional water tube member in accordance with claim 5 furtherincluding a blind manifold member coupled to the lower end of the Watertube member so as to permit a reversal of Water flow from the inner pipeto the outer pipe, and bifurcated coupling means connected to the upperend of the Water tube member to permit separate coupling of associatedconduits to the inner pipe and the outer pipe.

7. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a housing of substantially cylindrical form, aburner positioned at the base of said housing, a flue at the top of saidhousing, a Water tube member arranged in a Vertically disposed hourglassconfiguration between the burner and the flue with the top and bottomportions of said hourglass configuration adjacent the housing to blockthe passage of combustion gases thereby and having a bafile memberpositioned across the narrow portion of the hourglass configuration,said Water tube member including concentric portions for thebidirectional conduction of water therein and having a blocking memberterminating the lower end of the Water tube member in a manner such asto permit the reversal of Water flow thereat within the Water tubemember and further having a coupling member connected to the upper endthereat for admitting water to flow into an inner concentric portion ofthe Water tube member and for permitting the flow of water out of theouter concentric portion of said water tube member, and means connectingthe inlet side of the coupling member directly to a water recirculatingpump and the outlet side of the coupling member to a Water return lineto the swimming pool in order to promote the Water flow through theheater at a maximum rate of flow.

8. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a combustion chamber having an inner wall, aburner positioned at the base of said chamber, a flue at the top of saidchamber, a water tube member arranged in a vertically disposed hourglassconfiguration between the burner and the flue with the top and bottomportions of said hourglass configuration adjacent the inner wall of thecombustion chamber to block the passage of combustion gases thereby andhaving a baflle member positioned across the narrow portion of thehourglass configuration, said water tube member comprising an inner tubepositioned within an outer tube along substantially the entire length ofthe water tube member and having a blind manifold terminating the lowerend of the water tube member in a manner such as to transfer water fromthe inner tube to the outer tube, and a coupling member connected to theupper end of the water tube member for admitting water to flow into theinner tube and for permitting the flow of water out of the outer tube.

9. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a combustion chamber having an inner wall, aburner positioned at the base of said chamber, a flue at the top of saidchamber, a water tube member arranged in a vertically disposed hourglassconfiguration between the burner and the flue with the top and bottomportions of said hourglass configuration adjacent the inner wall of thecombustion chamber to block the passage of combustion gases thereby andhaving a baflie member positioned across the narrow portion of thehourglass configuration, said Water tube member comprising an inner tubepositioned within an outer tube along substantially the entire length ofthe water tube member and having a blind manifold terminating the lowerend of the water tube member in a manner such as to transfer water fromthe inner tube to the outer tube, a coupling member connected to theupper end of the water tube member for admitting water to flow into theinner tube and for permitting the flow of water out of the outer tube,and means connecting the coupling member directly between a waterrecirculating pump and the swimming pool to permit the maximum rate offlow of water through the water heating apparatus.

10. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a housing, a burner, and an exhaust stackarranged in a heater configuration, a water tube member coiled in anhourglass configuration between the burner and the exhaust stack withthe upper and lower portions of the hourglass configuration beingpositioned adjacent the housing to block the passage of combustion gasesthereby and having a baffle member positioned across the narrow portionof the hourglass configuration, said Water tube member comprising aninner tube positioned within an outer tube along at least a portion ofthe extent of the outer tube, and means for admitting water to saidinner tube for preheating prior to its transfer to the outer tube fromthe inner tube comprising a conduit coupled to the inner tube and havingan opening permitting a limited flow of water to the region of the outertube outside the inner tube.

11. Water heating apparatus for use in conjunction with a swimming poolor the like comprising a housing, a burner, and an exhaust stackarranged in a heater configuration, a water tube member positionedwithin the heater housing between the burner and the exhaust stack andcomprising an inner tube positioned within an outer tube along at leasta portion of the extent of the outer tube, and means for admitting waterto said inner tube for preheating prior to its transfer to the outertube from the inner tube and to the region of said outer tube outsidesaid inner tube at a limited rate of flow such as to prevent overheatingof water in said region.

12. A water heating device for use in a swimming pool Water heater orthe like comprising an outer pipe containing an inner pipe, and acoupling member having means for admitting water principally to saidinner pipe while admitting a limited flow of water to the region of theouter pipe outside the inner pipe to prevent overheating of water insaid region.

References Cited by the Examiner UNITED STATES PATENTS 1,033,588 7/1912Hopkins 126362 1,046,842 12/ 1912 Oflutt -66 2,474,401 6/ 1949 Mustee122-250 2,633,108 3/ 1953 Sterick 122250 3,118,430 1/1964 Russell et al.122--250 FOREIGN PATENTS 1,263,899 5/ 1961 France.

269,816 4/ 1927 Great Britain.

337,556 5/ 1959 Switzerland.

FREDERICK L. MATTESON, JR., Primary Examiner.

ROBERT A. DUA, Examiner.

1. WATER HEATING APPARATUS FOR USE IN CONJUNCTION WITH A SWIMMING POOLOR THE LIKE COMPRISING A HOUSING OF SUBSTANTIALLY CYLINDRICAL FORM, ABURNER POSITIONED AT THE BASE OF SAID HOUSING, A FLUE AT THE TOP OF SAIDHOUSING, AND A WATER TUBE MEMBER ARRANGED IN A VERTICALLY DISPOSEDHOURGLASS CONFIGURATION BETWEEN THE BURNER AND THE FLUE WITH THE TOP ANDBOTTOM PORTIONS OF SAID HOURGLASS CONFIGURATION ADJACENT THE HOUSING TOBLOCK THE PASSAGE OF COMBUSTION GASES THEREBY AND HAVING A BAFFLE MEMBERPOSITIONED ACROSS THE NARROW PORTION OF THE HOURGLASS CONFIGURATION,SAID WATER TUBE MEMBER INCLUDING CONCENTRIC PORTIONS FOR THEBIDIRECTIONAL CONDUCTION OF WATER THEREIN AND HAVING A BLOCKING MEMBERTERMINATING THE LOWER END OF THE WATER TUBE MEMBER IN A MANNER SUCH ASTO PERMIT THE REVERSAL OF WATER FLOW THEREAT WITHIN THE WATER TUBEMEMBER AND FURTHER HAVING A COUPLING MEMBER CONNECTED TO THE UPPER ENDTHEREOF FOR ADMITTING WATER TO FLOW INTO